1. Field of the Invention
The present invention relates to an apparatus and method for cleaning a read and/or write head of a machine, such as a tape drive, which is adapted to operate on a tape cassette containing a magnetic tape, and more particularly to such an apparatus and method which is particularly adapted to clean such a head where the head has irregularities on its operating surface.
2. Background Art
There are various machines which operate to receive information from, or impart information to, magnetic tape. Two such commonly used machines are video player/recorder units and audio player/recorder units. In the video units, the magnetic tape is pulled outwardly from a cassette tape cartridge and brought into engagement with a shallow cylindrical surface of a rotating element on which the player/recorder head is carried. In the audio unit, the magnetic tape generally extends across a forward portion of the tape cassette, with the tape being exposed at this forward portion. The tape passes by a stationary player/recorder head, and is also engaged by a capstan and pinch roller of the machine to cause the tape to move along its length.
Various cleaning devices have been proposed to clean the operating surfaces of such player/recorder units. With the video unit, it has been a common practice to provide a cleaning ribbon which is engaged by guide elements in the video player/recorder unit to carry the cleaning ribbon into engagement with the rotating element carrying the playing/recording head and possibly into engagement with other components of the video player/recorder unit.
Another type of cleaning mechanism which is used more commonly with audio player/recorder units comprises a cassette housing which carries a cleaning member which in turn is adapted to carry a cleaning element, such as a pad. This cleaning member is arranged to move on a cleaning path, which in many cleaning devices is a back and forth path where it wipes against the playing/recording head of the audio unit. Quite commonly, the cleaning member is driven on its back and forth path through a suitable drive transmission from one of the drive spindles in the audio player/recorder unit.
To obtain the proper cleaning action, it is desirable to have adequate frictional engagement between the cleaning pad and the surface of the player/recorder head of the audio unit. However, if the force of the frictional engagement is excessive, then the resistance imparted back through the drive transmission to the drive sprocket may trigger the automatic shutoff mechanism in the machine.
Another concern is that the operating surface of the player/recorder head is quite often not a flat surface, but a moderately curved surface. Also, in some instances, the operating surface of the head may be a compound curved surface, having two side curved portions, with a moderate recess between the two curves. This may have a tendency to create a resisting force against the cleaning pad greater than what would normally be encountered simply from frictional engagement.
Another consideration is that the location of the player/recorder head will vary from machine to machine. Thus, the cleaning element (i.e. usually the cleaning pad) must be mounted in such a way that it can be positioned at different forward to rear locations and still be in proper cleaning engagement with the player/recorder head.
One common means of mounting the cleaning element is to place it on an arm which is pivotally mounted for back and forth motion about a pivot location located in the center portion of the cassette housing. To accommodate different forward to rear locations of the cleaning element, there is sometimes provided a string arm, which in one form can be a U-shaped spring section, such as shown in U.S. Pat. No. 4,225,893--Loiselle. This same patent shows another method of accommodating this difference in forward to rear location of the cleaning element is to mount the forward to rear lever arm itself by means of a pin and slot connection so that it can be positioned at different forward to rear locations as the pivot arm swings back and forth about the pivot location to accomplish the cleaning motion.
With regard to the problem of the cleaning element being "caught" or "snagged" on the surface of the playing/recording head (e.g. possibly being engaged by a side surface portion of the head so as to create a relatively large resistance to the back and forth movement of the cleaning element), one approach to this problem, as shown in U.S. Pat. No. 4,454,551--Clausen et al, is to provide the arm which carries the cleaning pad with a spring having a somewhat "Z" configuration, where the spring has two oppositely positioned U-shaped spring sections.
In yet other instances, the cleaning element is mounted to a carrier which, instead of a pivot motion, has a linear side to side motion, with the carrier or carriage for the cleaning pad having a laterally extending member mounted between pins. An example of this is shown in U.S. Pat. No. 4,442,468--d'Alayer de Costemore d'Arc.
In addition to video and audio playing/recording units, there are also tape drives which move a magnetic tape relative to a read/write head so that data can be taken from the tape or transmitted to the tape. In one such tape drive, which is sold by Hewlett Packard as the HP 9144A Tape Drive, there is provided a read/write head which is positioned at a front side location relative to the tape cassette, and the operating surface of this head has a pair of vertically oriented ridges which protrude outwardly from the operating surface a short distance. With regard to cleaning such a read/write head, for example by a back and forth motion of a pad, these ridges aggravate the problem of the cleaning pad encountering an excessive resisting force by the pad coming into engagement with the side surfaces of these ridges.
In this tape drive machine, there is a drive wheel (i.e. a capstan) which engages a drive element in the tape cassette to cause rotation of the tape. The operation of the machine is such that the motion imparted to the tape is a somewhat erratic back and forth motion.